With the popularization of broadband access and the rapid development of streaming media-based broadband applications, the CDN (Content Delivery Network, content delivery network) is found an effective means of effectively mitigating pressure exerted on a backbone network by high throughput of streaming media transmission and improving quality of service of the streaming media. A core idea of the CDN is that a new layer of network architecture is added in the current Internet, and content of a website is published at a network “edge” closest to a user, so that the user may obtain needed content nearby, that is, multiple cache nodes are set in the network, content of one server is evenly distributed to the multiple cache nodes, and the user obtains the content from the closest cache node. In this manner, a problem of a low response speed that occurs when a user visits a website, where the problem is caused by a narrow network bandwidth, heavy traffic of user visits, and uneven distribution of network nodes, is solved, thereby increasing the response speed when a user visits a website.
Storage space of a cache node includes two parts: one part storing the most popular content for access by a local user, and the other part storing content which is involved in collaboration for access by other cache nodes.
If access of the local user does not need to go through a backbone network, but access in the collaboration needs to go through the backbone network, when an output link from a cache node to the backbone network is congested, the collaboration among cache nodes makes the output link from the cache node to the backbone network more congested, thereby reducing a bandwidth utilization rate of the whole network.